The overall goal of Clinical Research Core B is to support the individual projects and the overall specific Aims proposed in this Program Project. This goal will be accomplished by providing long-term follow-up of an established cohort of patients who have Barrett?s esophagus in which longitudinal investigations of the development of esophageal cancer are conducted. The Seattle Barrett's Esophagus Program (the patient base for Core B) has an established cohort of 325 active participants who have Barrett's esophagus and who are in various stages of progression to cancer. These patients are in periodic endoscopic biopsy surveillance for detection of esophageal adenocarcinoma when it is early and curable with surgery. The lifetime risk of developing cancer in Barrett's esophagus is low, estimated to be in the range of 5-10 percent. However, the Seattle Barrett's Esophagus Program specializes in the surveillance of high-risk patients. More than 25 percent of the Program cohort has an estimated 5-year cancer risk of 28-59 percent and the Program gets regular referrals of these patients because it is difficult for them to be safely or practically managed in the community. Core B, therefore, consists of a substantial number of both high-risk and low-risk patients, providing a unique resource for the conduction of investigations of progression to cancer. Core B is essential to the Program Project. All data generated by the individual Projects can be linked directly to a specific endoscopy, biologic specimen or patient interview coordinated by Core B. The specific Aims of Core B are: (1) To obtain longitudinal tissue samples from Barrett's epithelium for histologic diagnoses and coordinate the acquisition of the corresponding research biopsies, gastric fluid aspirates and blood samples from the Same patients for molecular biologic and epidemiologic investigations as proposed in Projects 1, 2, and 3; (2) To provide long-term follow-up of a large cohort of patients for molecular genetic investigations (Projects 1 and 3), the outcomes of which may result in novel endpoints for epidemiologic investigations (Project 2) and provide scientific rationale for chemopreventive therapies; (3) To continue to recruit new patients to the Program by referral from community gastroenterologists, thus, maintaining a large well-characterized cohort of patients for the investigations proposed in Projects 1, 2 and 3.